JP5599298B2 - Sound absorption duct - Google Patents

Description

  The present invention relates to an improvement in a sound absorbing duct that is piped on the ceiling or the like of a building and performs ventilation in the room and ventilation for cooling and heating the room.

  In recent years, buildings having airtightness are generally built to improve the living environment, and accordingly, it is required to stably ventilate and heat / heat the airtight room. In order to satisfy such requirements, ducts are arranged using the ceiling and walls of buildings and the like, and external air from a blower source such as a blower is supplied into the room through the duct, or between upper and lower layers. Although an air supply system that circulates air is used, noise generated by driving a blower or the like and wind sound when circulating in the duct are propagated through the duct into the room and give unpleasant feeling.

  For this reason, for example, as described in Patent Document 1, a tubular inner wall made of a sheet-like material having air permeability such as a non-woven fabric, and the outer peripheral surface of the inner wall are spirally wound at a constant pitch. A rigid synthetic resin reinforcing strip, and a band-like closed-cell synthetic resin material having a certain thickness interposed between adjacent reinforcing strips. A tubular heat insulating layer provided with a large number of sound absorbing holes penetrating between the inner and outer peripheral surfaces of the closed foam synthetic resin material at predetermined intervals in the circumferential direction, and a non-breathable soft synthetic resin sheet covering the heat insulating layer A sound-absorbing duct composed of an outer wall is being developed.

  According to this sound absorbing duct, the tubular heat insulating layer made of an independent foamed synthetic resin material provides a heat insulating function, and sound waves enter the sound absorbing holes provided in the heat insulating layer through the fine ventilation holes provided in the inner wall made of nonwoven fabric or the like. When entering, the sound energy is attenuated and the inner wall part that closes the sound absorption holes vibrates to produce sound absorption. Sound waves enter the space inside the sound absorption holes from the fine ventilation holes provided in the nonwoven fabric. When this occurs, the sound wave diffuses rapidly, and the sound in the sound absorbing hole is vibrated while being diffusely reflected by the peripheral wall of the sound absorbing hole, thereby exerting a silencing effect.

JP 2006-313043 A

  However, according to the above sound absorbing duct, as shown in FIG. 7, the sound absorbing holes 15 provided in the heat insulating layer 13 made of an independent foamed synthetic resin material are formed in a circular hole shape having a constant diameter over the entire length. Therefore, when the hole wall of the sound absorbing hole 15 is assumed to be a smooth surface, the sound wave a that has entered the sound absorbing hole 15 through the ventilation hole of the inner wall 11 made of nonwoven fabric is reflected when the sound absorbing hole 15 is incident on the hole wall. Since it reaches the inner surface side of the outer wall 14 while sequentially reflecting on the opposite wall surface until it passes through the sound absorption hole 15 at the same angle as the angle, the number of reflections of the sound wave a cannot be changed in the increasing direction. The sound absorption effect due to the vibration of air during reflection cannot be sufficiently expected, and the outside opening diameter of the sound absorption hole 15 facing the inner surface of the outer wall 14 has the same diameter as the inside, so the light is emitted from the sound absorption hole 15. The sound wave a is reflected by the inner surface of the outer wall 14 and again becomes a sound absorbing hole. There is a problem that it becomes easy to return to 12 and the mute function is lowered.

  In addition, the heat insulation layer made of closed-cell synthetic resin has a structure that is divided by the reinforcing strips without being continuous in the length direction of the tube, so that not only the heat insulation effect is impaired, but also the adjacent belt-like independent Since the foamed synthetic resin material is spirally wound in a state where the opposite end surfaces are simply joined without being integrally connected to each other by fusion or the like, when this duct is bent, between the opposite end surfaces There is a problem that a gap is generated and the heat insulation function is lowered.

  The present invention has been made in view of such problems, and the object of the present invention is to effectively absorb and mute noise generated from an air source such as an air blower and the sound of wind flowing through the inside with a simple structure. It is possible to provide a sound-absorbing duct that can perform a good heat insulating function.

In order to achieve the above object, a sound absorbing duct according to the present invention is provided with a tubular inner wall made of a non-woven fabric having air permeability and a spiral wound around the outer peripheral surface of the inner wall at a constant pitch. A synthetic resin reinforcing strip material, a tube wall formed of an independent foam synthetic resin layer provided in a tubular shape over the entire length of the outer peripheral surface of the inner wall via the reinforcing strip material, and the tube wall The outer wall is made of a non-breathable soft synthetic resin sheet that covers the outer peripheral surface. A sound-absorbing duct that is perforated at small intervals in the vertical direction, and the above-mentioned tube wall is spirally wound with a band-shaped material made of an independently foamed synthetic resin having a certain width and thickness, while joining opposite side end surfaces. The outer wall has a constant width A soft synthetic resin strip having a layer of material that is overlapped without being heat-sealed to the outer surface of the above-mentioned independent foam synthetic resin strip and spirally wound integrally with the independent foam synthetic resin strip and on one side thereof The end portion was interposed between the opposing end surfaces of the adjacent foamed synthetic resin belt-like material, and was fixed integrally to these opposing end surfaces by heat fusion, and the other end portion was wound in a single roll first. Heat-sealed to one end of a soft synthetic resin strip on the independent foam synthetic resin strip, and the sound absorbing hole is a cone that tapers from the inner peripheral surface to the outer peripheral surface of the tube wall. It is formed in a shape or a pyramid shape.

  In the sound absorbing duct configured as described above, the invention according to claim 2 is provided with two layers of tube walls, an inner tube wall and an outer tube wall made of a closed foam synthetic resin layer, between the inner wall and the outer wall. It is characterized by that.

  According to the first aspect of the present invention, since the inner wall of the duct for ventilating is formed from a breathable nonwoven fabric, innumerable voids between the fibers of the nonwoven fabric perform a sound absorbing action equivalent to that of the porous sound absorbing material. In addition to being able to effectively absorb mid to high range sounds, a tube made of an independent foamed synthetic resin layer between the inner wall made of this non-woven fabric and the outer wall made of a non-breathable soft synthetic resin sheet Since a wall is provided and a number of sound absorbing holes penetrating between the inner and outer peripheral surfaces are formed in the pipe wall at small intervals in the circumferential direction and in the length direction, sound waves are generated from the gaps between the small fibers of the nonwoven fabric. When entering the sound absorbing holes, the air layer in the sound absorbing holes exhibits a silencing effect similar to that of a resonator by oscillating the air in the sound absorbing holes while diffusely reflecting at the hole walls of the sound absorbing holes. Can absorb and mute even low-frequency noise. Kill.

  At this time, since the sound absorbing hole is formed in a conical shape or a pyramid shape that tapers from the inner peripheral surface to the outer peripheral surface of the tube wall, the hole wall is coupled with the inclination toward the outer side so that the hole wall faces the outer side. Since the interval between the opposing wall surfaces of the wall gradually decreases from the inner wall side to the outer wall side, the reflection angle of the sound wave incident on the sound absorbing hole through the inner wall made of nonwoven fabric changes as it goes toward the outer wall side. In addition, the number of reflections increases and the foam film of the independent foam synthetic resin layer frequently vibrates in the air to provide an excellent silencing effect, and in addition, the outer opening diameter of the sound absorbing hole facing the inner peripheral surface of the outer wall Because of the small diameter, the sound wave emitted from the opening end is difficult to return to the sound absorption hole, and is excluded to the outside through a gap between the inner peripheral surface of the outer wall and the outer peripheral surface of the tube wall. Can be provided.

Furthermore, since the tube wall is formed of an independent foamed synthetic resin layer, it exhibits excellent heat insulation and is made of a synthetic resin that is spirally wound around the outer peripheral surface of the inner wall made of nonwoven fabric with a constant pitch. The reinforcing strip can provide pressure resistance as well as shape retention, and a sound absorbing duct with easy handling and workability can be obtained.
In addition, according to the present invention, a tube wall is formed by spirally winding a band-shaped material made of an independent foamed synthetic resin having a certain width and thickness while joining opposite side end surfaces to each other, and the outer wall is constant. A flexible synthetic resin strip having a width is superposed on the outer surface of the above independent foam synthetic resin strip without being heat-sealed, and spirally wound integrally with the independent foam synthetic resin strip. One end is interposed between the opposing end faces of the adjacent foamed synthetic resin strips, and is fixed to these opposing end faces by heat fusion, and the other end is wound in a single roll first. Since it is heat-sealed to one end of the soft synthetic resin strip on the rotated independent foam synthetic resin strip, the heat insulating layer made of the independent foam synthetic resin strip forming the tube wall However, it has a good thermal insulation function continuously in the length direction of the pipe. Of course, the opposing side end surfaces of the adjacent foamed synthetic resin strips can be integrally heat-sealed through one side end of the soft synthetic resin strip covering the strips. Therefore, even if the duct is bent, there is no possibility that a gap that lowers the heat insulation function is generated between the opposing side end faces of the belt-like material.
Furthermore, the soft synthetic resin belt-like material covering the independent foam synthetic resin belt-like material is overlapped without heat-sealing the portions other than the both end portions on the outer surface of the independent foam synthetic resin belt-like material. Since the bending resistance of the duct made of a soft synthetic resin strip is lowered and the circular cross section is maintained, the duct can be easily and greatly bent, so that not only the workability is improved, but also independent. A gap is formed between the outer peripheral surface of the tube wall formed by spirally winding the foamed synthetic resin strip and the inner peripheral surface of the outer wall formed by spirally winding the soft synthetic resin strip on the outer peripheral surface. Therefore, a large number of sound waves reaching the small-diameter opening end of the sound absorption hole while being diffusely reflected in the cone-shaped or pyramid-shaped sound absorption hole drilled in the tube wall in large numbers can be generated from the opening end. Introducing the outer wall Attenuation while diffusely reflected in the opposing wall of the tube wall can be silenced.

  Further, as in the invention described in claim 2, an inner side composed of an independent foamed synthetic resin layer in which a large number of sound absorbing holes are provided between the inner wall composed of the nonwoven fabric and the outer wall composed of a non-breathable soft synthetic resin sheet. If two layers of tube walls, the tube wall and the outer tube wall, are provided, the sound wave can be diffusely reflected in the gap between the sound absorbing hole provided in these tube walls and the inner and outer tube walls. A duct having a silencing effect and a heat insulating effect can be provided.

The perspective view of the sound-absorbing duct which cut a part in radial direction and length direction. The longitudinal side view which cut the upper half part. A partly enlarged vertical side view. The expanded vertical side view of the sound-absorption hole part which shows the irregular reflection state of a sound wave. The longitudinal side view which cut the upper half part of the sound absorption duct which has provided the inner and outer two-layer pipe wall. The enlarged vertical side view of the part. The expanded vertical side view which shows the shape of the sound absorption hole of the conventional sound absorption duct.

  A specific embodiment of the present invention will be described with reference to the drawings. In FIGS. 1 to 3, a sound absorbing duct A is a thin tubular inner wall 1 having a constant diameter formed by a sheet-like material having air permeability made of a nonwoven fabric. And a reinforcing strip 2 made of a hard synthetic resin having a constant thickness and a constant width, which is spirally wound around the outer peripheral surface of the inner wall 1 at a constant pitch, and the reinforcing strip 2 A tube wall 3 made of an independent foamed synthetic resin layer having a constant thickness covering the outer peripheral surface of the inner wall 1 over the entire length thereof, and the entire outer peripheral surface of the tube wall 3 And an outer wall 4 made of a non-breathable soft synthetic resin sheet covering the tube, and further, a large number of pipe walls 3 made of the above independent foamed synthetic resin layer penetrate between the inner and outer peripheral surfaces of the tube wall 3. The conical sound absorbing holes 5, 5... The cone-shaped sound absorbing hole 5 has a large-diameter opening end side on the outer peripheral surface of the inner wall 1 and a small-diameter opening end side on the inner peripheral surface of the outer wall 4. To face. The sound absorption hole 5 has an opening diameter on the large diameter side of about 2 to 3 mm and an opening diameter on the small diameter side of about 1 to 1.5 mm.

  As the non-woven fabric forming the inner wall 1, a long strip-shaped non-woven fabric made of a synthetic resin fiber or natural fiber such as polypropylene or polyester and having a width substantially equal to the helical winding pitch of the reinforcing strip 2 is spirally formed first. The inner wall of the duct having a constant diameter is formed by spirally winding the belt-like nonwoven fabric portion 1a wound next to the next and the spirally wound belt-like nonwoven fabric portion 1a on the opposite side ends and heat-sealing. 1 is formed. Further, the reinforcing strip 2 is made of an olefin-based hard synthetic resin such as polypropylene and polyethylene having moderate flexibility and elasticity, and the side end portions of the adjacent strip-shaped nonwoven fabric portions 1a and 1a of the inner wall 1 that overlap each other. It is wound in a spiral with a constant pitch, with its inner surface overlaid and thermally fused. The cross-sectional shape of the reinforcing strip 2 is not limited to a rectangular shape, and may be an appropriate shape such as a semicircular shape or an elliptical shape.

  The tube wall 3 is made of a closed foam synthetic resin such as a foamed polyethylene resin, a cross section having a constant thickness substantially the same width as the belt-shaped nonwoven fabric forming the inner wall 1 is formed in a horizontally long parallelogram, and A strip-shaped material made of an independent foamed synthetic resin having a large number of conical sound absorbing holes 5 formed at small intervals in the width direction and the length direction is provided on the outer peripheral surface of the inner wall 1 made of nonwoven fabric. 2 is a spirally wound synthetic resin strip 3a which is spirally wound so as to cover 2 and a closed foamed synthetic resin strip 3a which is spirally wound next to each other. 3a2 is formed into a tubular shape by being spirally wound at the same pitch as that of the belt-shaped nonwoven fabric while being joined in a butted manner.

  Further, the outer wall 4 is made of a soft synthetic resin belt-like material such as polyethylene resin having a constant width wider than the width of the independent foam synthetic resin belt-like material forming the tube wall 3. Independently foamed synthetic resin belt-shaped material part 3a, which is first spirally wound in a state of being superposed on the material without being heat-sealed, and then, an independent foamed synthetic resin belt-shaped material part which is wound once spirally The soft synthetic resin strip member 4a which is superimposed on the independent foam synthetic resin strip member 3a between the outward inclined side end surface 3a1 and the inward inclined side end surface 3a2 which are joined to each other in abutment with each other. One side end portion 4a1 is interposed, and the joint-inclined synthetic resin belt-shaped material portions 3a, 3a adjacent to each other through the one side end portion 4a1 are integrally heat-sealed to the inclined side end surfaces 3a1, 3a2. At the same time, the other end 4a2 of the soft synthetic resin strip-shaped member 4a is spirally wound first. Those formed by integrally fixed by the heat-sealed on one side outer surface of the soft synthetic resin-made belt material portion 4a on the closed-cell foam plastic strip material portion 3a. Accordingly, the portions other than the both end portions of the soft synthetic resin strip-shaped material portion 4a are simply overlapped with each other without being thermally fused to the outer surface of the independent foam synthetic resin strip-shaped material portion 3a.

  The sound absorbing duct configured as described above can be manufactured by the same manufacturing method as that of a normal synthetic resin flexible tube. Briefly describing the production method, a strip-shaped nonwoven fabric having a certain width is wound on the rotating shaft for molding, and then wound in a single turn on one end of the strip-shaped nonwoven fabric portion 1a wound in a single roll. The inner wall 1 is formed by spirally winding the other side end of the belt-shaped nonwoven fabric portion 1a that overlaps or abuts, and a semi-molten synthetic resin reinforcing strip 2 is extruded from a molding nozzle. On the superposed part of the belt-like non-woven fabric part 1a, it is spirally wound on the superposed part or the butt part, and the superposed part or butt part of the belt-like non-woven part is fused by the melting temperature and cooled in that state. Alternatively, it is fixed integrally on the butt portion. Note that a plurality of reinforcing strips 2 ′ having a diameter smaller than that of the reinforcing strip 2 are spirally wound on a strip-shaped non-woven fabric forming the inner wall 1 in a plurality of parallel and parallel states.

  Furthermore, the small-diameter portion of the sound absorbing hole 5 in the independent foamed synthetic resin belt-shaped material having a constant thickness of a transversely long parallelogram shape in which the sound absorbing holes 5 are provided at small intervals in the width direction and the length direction is opened. On the above-mentioned strip-shaped nonwoven fabric that is spirally wound prior to the independent foam synthetic resin strip material on the molding rotation axis while superposing a wider range of soft synthetic resin strip materials than the closed foam synthetic resin strip material on the outer surface side Next, the inwardly inclined synthetic resin strip-shaped material portion 3a wound in a spiral manner on the outwardly inclined synthetic resin-made strip-shaped material portion 3a1 wound spirally first, and then the inwardly inclined synthetic resin strip-shaped material portion 3a wound in a spiral shape. 3a2 are joined so as to abut each other, and one side end portion 4a1 of the above-mentioned soft synthetic resin belt-like material that is superimposed on the previously wound synthetic foam synthetic resin belt-like material is joined while being semi-molten by heating. It is interposed between the inclined side end faces 3a1 and 3a2. Rukoto by the soft synthetic resin-made belt material of one side end portion 4a1 independently foamed synthetic resin strip material portion 3a which is bonded via a fused side end surface of 3a 3a1, 3a2 with each other together, fixed.

At the same time, other than the soft synthetic resin strip on the independent foam synthetic resin strip wound next on one side of the soft synthetic resin strip on the previously wound synthetic foam strip The side end 4a2 is made into a semi-molten state by heating, and is fused and fixed together. In this way, the independent foamed synthetic resin belt-like material in which the soft synthetic resin belt-like material is superposed on the outer surface via the reinforcing strip 2 on the outer peripheral surface of the inner wall 1 is placed between the inclined side end faces 3a1, 3a2 facing each other. One side end 4a1 of the strip material made of soft synthetic resin
Between the outer surfaces of the independent foamed synthetic resin strips 3a and 3a on the inclined end surface of the closed foam synthetic resin strip to be thermally fused. The sound-absorbing duct A is manufactured by spiral winding while heat-sealing through the other end 4a2 of the band-shaped material. It should be noted that the inner surface of the independent foamed synthetic resin strip-shaped material portion 3a on which the reinforcing strip 2 is superimposed is elastically recessed and deformed along the surface of the reinforcing strip 2 to cover the reinforcing strip 2. ing.

  The sound absorption duct A thus obtained is piped on the ceiling of a house, etc., and performs ventilation, cooling and heating of the room through the sound absorption duct A from an air source such as a blower. The tube wall 3 not only exhibits excellent heat insulation over the entire length, but also noise generated by driving a blower or the like and wind sound when circulating in the duct pass through the nonwoven fabric forming the duct inner wall 1. The sound energy is converted into thermal energy by friction with the nonwoven fabric and vibration of the nonwoven fabric fibers, thereby producing a silencing effect.

  Furthermore, when the sound wave a enters the sound absorbing hole 5 provided in the tube wall 3 made of an independent foamed synthetic resin through the gap between the small fibers of the nonwoven fabric, it rapidly diffuses to form the hole wall surface of the sound absorbing hole 5. The air in the sound absorption hole 5 is vibrated by being irregularly reflected by a fine uneven surface caused by a large number of air bubbles, so that noise can be absorbed and silenced. Moreover, the sound absorption holes 5 gradually become smaller in diameter from the inner opening end facing the inner wall 1 made of nonwoven fabric toward the outer opening end facing the outer wall 4 made of a non-breathable soft synthetic resin sheet. Since it is formed in a conical shape, as shown in FIG. 4, as the sound wave a incident in the sound absorbing hole 5 moves toward the outer wall 4, the interval width of irregular reflection at the hole wall of the sound absorbing hole 5 becomes narrower and the number of times. And the sound absorbing action due to irregular reflection is more effectively performed, and the sound wave emitted from the small diameter opening end of the sound absorbing hole 5 toward the inner surface of the outer wall 4 is difficult to return into the sound absorbing hole, and the inner peripheral surface of the outer wall It can be excluded to the outside through a gap with the outer peripheral surface of the tube wall, and an extremely quiet indoor environment can be created.

  In addition, the independent foamed synthetic resin belt-like material is formed in a state where the soft synthetic resin belt-like material for forming the outer wall is superposed on the outer surface of the independent foamed synthetic resin belt-like material forming the tube wall 3 without being thermally fused. When the tube wall 3 and the outer wall 4 are formed by spirally winding the material, the strip-shaped material portion 3a made of the closed foam synthetic resin that has been spirally wound first, and then the closed foam synthetic resin that has been spirally wound. Since the side end portions 4a1 and 4a2 of the above-mentioned soft synthetic resin strip-like material are heat-sealed to the joined portions while joining the inclined side end faces 3a1 and 3a2 facing the strip-like piece portion 3a, this sound absorbing duct A Even if it is bent when bending, the tube wall 3 made of an independent foamed synthetic resin can maintain a continuous state in the long direction and exhibit the desired heat insulation effect, and can also be compressed in the length direction. On the inner duct wall that curves in a concave arc shape where force acts May be the outer wall 4 by the compression force absorbs the compressive force while being deformed to wrinkled, easily construction is in a state of even holding the circular cross section at the bending processed portion.

  In the above embodiment, a tube wall 3 made of an independent foamed synthetic resin is provided between the inner and outer walls 1 and 4, but as shown in FIGS. 5 and 6, the inner tube wall 3A and the outer tube wall are provided. A structure in which two layers of 3B are stacked in a double tubular shape may be used. The inner and outer tube walls 3A and 3B are provided with sound absorbing holes 5 that gradually become smaller in diameter from the inner peripheral surface side toward the outer peripheral surface side in the circumferential direction and the length direction at small intervals.

  When forming the above-mentioned double tube-shaped inner and outer tube walls 3A and 3B, the reinforcing strip 2 spirally wound at a constant pitch on the outer peripheral surface of the inner wall 1 formed by spirally winding a strip-like nonwoven fabric. In the inner tube wall 3A that is formed, only the independent foamed synthetic resin strip is overlapped without overlapping the soft synthetic resin strip on the outer surface of the independent foam synthetic resin strip that forms the inner tube wall 3A. On the outer peripheral surface of the inner wall 1, the independent foamed synthetic resin strip 3 a that is spirally wound next to the outwardly inclined side end surface 3 a 1 of the closed foam synthetic resin strip 3 a that is spirally wound first. The inner tube wall 3A is formed by spiral winding while joining the inwardly inclined side end surface 3a2 so as to abut each other without thermal fusion.

  On the other hand, on the outer foam synthetic resin strip that is spirally wound on the inner tube wall 3A, a soft synthetic resin strip wider than the closed foam synthetic resin strip is applied to the outer surface in the same manner as in the above embodiment. Overlapped. Then, the independent foaming that is next spirally wound on the outwardly inclined side end surface 3b1 of the independently foamed synthetic resin strip-shaped material portion 3b that spirally winds around the outer peripheral surface of the inner tube wall 3A that is formed in advance. One side end of the above-mentioned soft synthetic resin belt-shaped material that is joined so as to abut the inwardly inclined side end surface 3b2 of the synthetic resin belt-shaped material portion 3b and is superimposed on the previously wound synthetic foam synthetic resin belt-shaped material Independently foamed synthetic resin strip 3a joined via one side end 4a1 of this soft synthetic resin strip by interposing the part 4a1 between the inclined side end faces to be joined while being semi-molten by heating , 3a side end surfaces are integrally fused and fixed together, and one side edge of the above-mentioned soft synthetic resin strip material from the opposed side end surfaces of these independent foam synthetic resin strip members 3a, 3a joined together 4a3 is protruded inward in advance, and this protruding edge 4a3 is welded to the intermediate portion in the width direction on the outer surface of the inner tube wall 3A at the same time as the inner end wall 3A and the inner tube wall 3A. An outer tube wall 3B that is integrally connected via the protruding end edge 4a3 is formed. Since other structures are the same as those in the above embodiment, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  According to the sound absorbing duct A ′ configured as described above, in addition to the operational effects exhibited by the sound absorbing duct A having the tube wall 3 made of only one layer of the independent foam synthetic resin layer, the inner and outer double tube walls 3A and 3B In addition to exhibiting an excellent heat insulating effect, sound waves that have entered the sound absorbing holes 5 provided in the inner tube wall 3A through the inner wall 1 made of nonwoven fabric can be absorbed and silenced in the sound absorbing holes 5 in the same manner as described above. Above, the sound wave that has passed through the sound absorbing hole 5 is absorbed by being diffused through a gap between the inner and outer tube walls 3A and 3B, and further enters the sound absorbing hole 5 provided in the outer tube wall 3B from this gap. In the sound absorbing hole 5 as well, the sound in the gap between the inner peripheral surface of the outer wall 4 and the outer peripheral surface of the tube wall 3 is removed from the outer wall after vibrating the air in the same manner as described above to achieve a silencing effect. Is it an independent foamed synthetic resin while vibrating 4? It is sound absorption while diffusely reflected at the outer surface of the made tube wall 3 is capable of providing a duct may enable more quiet ventilation. In any of the above embodiments, the sound absorbing hole 5 is formed in a conical shape. However, it may be formed in a pyramid shape. In short, the diameter gradually decreases from the inner wall 1 side toward the outer wall 4 side. What is necessary is just to form in a hole.

A Sound absorption duct 1 Inner wall made of non-woven fabric 2 Reinforcement strip 3 Tube wall made of independent foam synthetic resin 4 Outer wall made of soft synthetic resin sheet 5 Sound absorption hole

Claims (2)

A tubular inner wall made of a non-woven fabric having air permeability, a reinforcing strip made of synthetic resin spirally wound around the outer peripheral surface of the inner wall at a constant pitch, and the inner wall through the reinforcing strip A tube wall made of an independent foamed synthetic resin layer provided in a tubular shape over the entire length on the outer peripheral surface, and an outer wall made of a non-breathable soft synthetic resin sheet covering the outer peripheral surface of the tube wall, and independently foamed synthetic and made of a resin layer tube wall into a number of sound-absorbing hole penetrating between the inner and outer peripheral surfaces in the circumferential direction and length direction a sound absorbing duct formed by drilled for each small interval, the tube wall is constant It is formed by spirally winding a band-shaped material made of an independent foamed synthetic resin having a width and a thickness while joining opposite side end faces, and the outer wall is formed of the band-shaped material made of a soft synthetic resin having a certain width. Heat fusion to the outer surface of a foamed synthetic resin strip In such a state that they are overlapped without being spirally wound together with the independently foamed synthetic resin belt-like material, and one side end thereof is interposed between the opposite side end surfaces of the adjacent independent foamed synthetic resin belt-like material. Heat fusion to one end of a soft synthetic resin strip on a closed foam synthetic resin strip that is secured to the opposite end face by heat fusion and the other end is wound in a single roll. Yes and wear, further, the sound absorbing duct the sound-absorbing holes, characterized in that it is formed in a conical shape or pyramidal shape tapers toward the outer peripheral surface from the inner peripheral surface of the tube wall.   2. The sound absorbing duct according to claim 1, wherein two layers of pipe walls, an inner pipe wall and an outer pipe wall made of a closed foam synthetic resin layer, are provided between the inner wall and the outer wall.

Images